Why not just let them go? Good question! You can adduce answers [such as] The American Mission, Unionism, Nationalism. Very few people in the North said, “Let them go.” Why? [To answer that] requires us to do what no historian has ever successfully done.

Foner’s inability to understand why Northerners were unwilling to let the South secede reflects his gigantic blind spot. He is unable to admit to himself that the reason Northerners wanted to “save” the Union lies in selfish economics, not altruistic abolitionism.

First, Southern cotton alone accounted for about two-thirds of all United States exports and all Southern exports represented about four-fifths of the country’s total. A truncated federal union composed solely of Northern states could not hope to maintain a favorable international balance of payments. The situation would be worse if the Northern states tried to match the anticipated low tariffs in the new Confederacy. Ten days before South Carolina led the cotton states into secession on December 20, 1860, the Chicago Daily Times editorialized on the calamities of disunion:

In one single blow our foreign commerce must be reduced to less than one-half what it now is. Our coastwise trade would pass into other hands. One-half of our shipping would be idle…We should lose our trade with the South, with all its immense profits. Our manufactories would be in utter ruins…If [our protective tariff] be wholly withdrawn from our labor…it could not compete with the labor of Europe. We should be driven from the market and millions of our people would be compelled to go out of employment.

Second, if the Confederacy were to survive as a separate country its import tariffs would certainly have been much lower than those of the federal union if the Northern states retained protective tariffs. President Jefferson Davis announced in his inaugural address, “Our policy is peace, and the freest trade our necessities will permit. It is…[in] our interest, [and those of our trading partners] that there should be the fewest practicable restrictions upon interchange of commodities.”

Low Confederate tariffs would confront the remaining states of the abridged Union with two consequences. First, since the federal tax base relied chiefly upon the tariff the government would lose the great majority of its tax revenue. Articles imported into the Confederacy from Europe would divert tariff revenue from the North to the South. Additionally, the Confederacy’s low duties would encourage Northern merchants to import European goods by smuggling them across the Ohio River, or the Northwestern states might secede themselves to form a third country in order to unilaterally set low import duties from the Southern Confederacy. Second, a low Confederate tariff would make Southerners more likely to buy manufactured goods from Europe as opposed to the Northern states where prices were inflated by protective tariffs.

Thus, after the opening shots at Fort Sumter the Northern states chose to fight to “preserve the Union” because they wanted to avoid the anticipated economic consequences of disunion—not because they had a mystical love for a Union with a people they hated. In January 1861 The Philadelphia Press editorialized, “It is the enforcement of the revenue laws, not the coercion of the state that is the question of the hour. If those laws cannot be enforced, the Union is clearly gone.” In When in the Course of Human Events author Charles Adams reasons:

If trade were to shift to the Southern ports because of a free trade zone, or extremely low duties relative to the North, then [the] great cities [of the Northeast] would go into decline and suffer economic disaster. The image painted by these editorials [from newspapers of Northeastern cities] is one of massive unemployment, the closing of factories and businesses, followed by unrest, riots, and possibly revolution. The inland cities of the North would also go into decline, like Pittsburgh, where duty-free British steel and iron products would cripple the American steel industry.

Foner’s depiction of Southern immorality leads him to the delusion that Northern war motivations could be nothing less than noble.

Most modern historians conscientiously search for the reasons the South seceded and than automatically assume those are the reasons for the Civil War. They are so obsessed with identifying the causes of secession they generally don’t stop to consider that the North could have let the South depart in peace and thereby avoided the War.

Due to that failure, many modern historians give little thought to the reasons that the North decided to coerce the South back into the Union. When they do attempt to come un with explanations, they generally ascribe it to a widespread desire to “preserve the Union” and thereby clothe it in a nobel but mystical feeling of kinship or something. Gary Gallagher is among those who have researched that angle the most. He admits that it is hard to get his students to understand why the concept of Union was so important. Their conclusions of their common sense is correct. The real reason that the Northern states would not permit the South to depart in peace was to avoid the economic consequences of disunion.

Tariffs were a major source of federal revenue in the 19th century. There were two types of tariffs: (1) ad valorum and (2) specific duty. The obvious question is, “Why two types?”

Ad valorum rates were a percentage of value. For example, if steel was imported at $25 a ton and the rate was 20% then the duty was $5.00. If, however, the price dropped to $20, the duty would be only $4.00. If instead the specific duty was $5.00 it would not change if the price os steel dropped to $20 a ton. It would remain $5 and at $20 per ton steel price it would essentially be a 25% tariff. Specific duty tariffs provided greater protection against price drops in the world market.